Facial aesthetics have an important influence on social behaviour and perception in our society. The purpose of the present study was to evaluate the effect of facial symmetry and inter-ocular distance on the assessment of facial aesthetics, factors that are often suggested as major contributors to facial aesthetics. The material consisted of 36 standardized facial photographs of patients (10-17 years of age) attending the orthodontic department. All except one were Caucasian. Eleven of these photographs (all Caucasian) were either left in their original form or modified by: (1) enlargement of the inter-ocular distance by 20 per cent; or (2) mirroring the right part of the face over the left part to obtain symmetry. Three series of 36 slides were composed, each including 11 modified slides or their unmodified counterparts. These were evenly distributed over the three series using a Latin square design. The photographs were assessed for their facial aesthetics using a visual ratio scale by a panel of 50 undergraduate dental and law students. The 11 modified/unmodified photographs enabled calculation of the effect of the modifications undertaken on the assessment of facial aesthetics. The scores of the 25 remaining photographs in each series were used as baseline data in order to estimate the inter- and intra-observer reproducibility. MANOVA and post-hoc t-test revealed significant differences between the unmodified and modified photographs (P < 0.001). The results show that symmetry and inter-ocular distance enlargement have a negative effect on facial aesthetics.